Effect of Na2O additions on the sinterability and piezoelectric properties of lead-free 95(Na0.5K0.5)NbO3–5LiTaO3 ceramics

As a candidate for lead-free piezoelectric materials, Na2O excess 95(Na0.5K0.5)NbO3–5LiTaO3 (NKN–5LT) ceramics were developed by conventional sintering process. Sintering temperature was lowered by adding Na2O as a sintering aid. Abnormal grain growth in NKN–5LT ceramics was observed with varying Na2O contents. This grain growth behavior was explained in terms of interface reaction-controlled nucleation and growth. The electrical properties of NKN–5LT ceramics were investigated as a function of Na2O concentration. In the 1 mol% Na2O excess NKN–5LT samples sintered at 1050 °C for 4 h in air, electromechanical coupling factor and piezoelectric constant of NKN–5LT ceramics were found to reach the highest values of 0.43 and 230 pC/N, respectively.